This invention relates to apparatus for supporting an object in a desired position and, more particularly, to novel and highly-effective apparatus whereby the position of copy or of a lamp, etc., can be easily and accurately adjusted without the aid of tensioning springs or the like.
There is often a need to adjust the position of copyholders, lamps, etc. In the case of copyholders, where one must read the copy held, the position selected will depend on factors including the size of the type to be read, the direction and intensity of the lighting, and the reflectiveness of the copy. In the case of lamps, the position selected will depend on factors including the intensity of the light produced by the lamp, the presence or absence of additional sources of light, and (in the case of a spotlight) the area of the spot at the distance of the object illuminated. In both cases, the position selected will depend upon other factors including the height, the visual acuity, and the personal preferences of the user of the apparatus.
All of the factors mentioned above are subject to change. For example, new copy may be substituted, ambient lighting conditions may change, the person using the apparatus may become fatigued, or a different person may use the apparatus.
Because of the importance of the problem, considerable attention has been given to it, and there are conventional devices for dealing with it. One such device comprises two pairs of arms. One pair is pivotally connected at one end to a first clamp bracket adapted to be secured to a support and at the other end to an adjustment bracket. The other pair of arms is pivotally connected at one end to a second clamp bracket adapted to support a copyholder or the like and at the other end to the same adjustment bracket. A single thumb knob control is provided at the point where one of the arms is pivotally connected to the adjustment bracket. To prevent the copy or lamp from sagging, notwithstanding tightening of the control knob, it is necessary to add tensioning springs to balance the weight of the apparatus. For example, each of a first pair of tensioning springs may have one end connected to the first clamp bracket and the other end connected to one of the arms of the first pair of arms mentioned above, and each of a second pair of tensioning springs may have one end connected to the adjustment bracket and the other end connected to an arm of the second pair.
The conventional solution is very useful and widely adopted, but the requirement for tensioning springs is obviously a drawback. Moreover, the position of the thumb knob precisely at the pivot between one of the arms and the adjustment bracket produces the result that the locking mechanism has a negligible mechanical advantage. A light accidental knock may be sufficient to cause unwanted repositioning of the copy or lamp even though the thumb knob is screwed down.